Lux Lacuna
by Ninjagrrl
Summary: Team 7 meet their new member, a neurologically altered, laser implanted assassin. Sai and Sakura centric science fiction AU. Loosely follows the Rescue Gaara arc and beyond.
1. Chapter 1

Lux Lacuna

Author's Notes- I was working on this huge Akatsuki science fiction AU, and since I find most things in life benefit from adding a little extra Sai, wrote him in. I don't think the original will ever get off the ground, but I managed to salvage quite a lot from Sai's appearance. It roughly follows the Rescue Gaara arc and beyond, with many parallel scenes and even more glaring omissions, becoming entirely Sai and Sakura-centric after the first few chapters.

Apologies for gratuitous use of "It's the future!" to justify the stuff I've invented. And the title is derived from words meaning light (lux) and empty/hole (lacuna). It turns out they're both Latin in origin, but I doubt that it literally translates.

Disclaimer- I don't own any of the recognisable characters or concepts. No profit is being made and no copyright infringement is intended.

Although the plot and characters are entirely Naruto-centric, this is set roughly in the Neuromancer world. I've made a fair few changes, invented some stuff, and completely disrespected both canons, but many of the terms, concepts and imagery are taken directly from William Gibson's canon. Please don't credit me for creating this universe!

* * *

_Jashinists_, Sakura thought when an explosion rocked the underground train and it bucked like a horse, the bottom blown half-out of the first carriage and those behind careening into it as it ground down hard on the tracks with a rusty metal squeal. The floor peeled back like a ribbon, sweeping up the crippled carriage in jagged metal ripples and slamming everything in between shut like a butterfly in a book.

Sakura was in the furthest carriage, facing away. Her back cracked hard against the wall, a taste of blood sweetly metallic in her mouth, and she was pinned flat as the momentum from behind shunted the broken carriage along the tracks. And then the first derailed as they left the tunnel, the impact spreading up the length like the crack of a whip, and Sakura threw herself down between seats as the carriage rolled slowly, lazily over and shuddered to a wounded halt as it bit deep into the walls.

Someone's luggage glanced off her shoulder and she ended up sprawled among the broken splintery remains of what had been the window, a dozen gashes opening almost painlessly. Sakura sat up, shards biting into her palms and the backs of her bare legs. The stuttering lights punctuated her vision in a series of violent white flashes, turned it to a handful of Polaroids full of blood and glass and magnesium-white emergency light. A sudden sense of disorientation overcame her then, as though her mind was still left behind and caught up in the slow spiral of the derailing train, not here sprawled among the broken glass.

And then she snapped back into herself, and heard the screaming, the calls for help and the sustained shrieks that did not expect anything, only cried out because there was too much pain to keep inside. The old fear rose for a moment as it always would do at times like this, but there was no Naruto and no Sasuke this time and had not been for years, and she picked herself up out of the broken glass and twisted seats.

Hands full of glass shards, gashed knees biting into the backs of the seats, she clawed her way out through the wreckage, to stand on what had been the window. The screams were rising, a dirty orange glow the colour of city lights silhouetting passengers crawling through the twisted corridors between the carriages. Sakura felt a faint panic beginning to stir as her eyes darted through the surreal scene, too many casualties to start saving them all, and then she pictured Tsunade standing there, brusque and competent among the chaos.

The doors and windows were in what had become floor and ceiling, the train lying on its side like a broken-backed snake. The wounded would not be able to escape that way. Sakura spun around with a musical squeal of grinding glass, climbing over the wreckage towards the end of the carriage. The flames would drive the passengers this way. All she had to do was find the way out.

There would be a full window in the second driver's compartment at the back of the train, and Sakura picked her way through the twisted metal and foam and glass towards it. The door frame had buckled out of shape under the impact. She climbed onto the seats and braced herself against the wall, throwing her whole weight on the handle as she tried to wrestle it from the jagged metal that held it there. Behind her, there was the brittle sound of someone blindly crawling in from the next carriage and falling onto glass, and she ignored that and the calls for help, no time to sit with someone and hold their hand if it meant that no one could escape.

Blood ran out between her fingers, hands beginning to slip on the slick metal. The gashes on her knees gaped again as Sakura pulled once more, something popping high in her shoulder, and then she glanced over her shoulder as she heard the gritty scrunch of someone land lightly among the broken glass behind her.

Someone was standing there, seemingly unwounded, watching her with a mild, almost calm curiosity. Sakura let her hands slip from the bloody handle and turned her attention to the boy. At first, she thought he was an android. He had the same placid, slightly lost look they always seemed to have stamped into them.

"Help me," she gasped, her breath coming ragged in the rising heat.

The boy's eyes flickered over her, and he nodded. He stepped towards her, walking lightly through the broken seats and drifts of luggage, reaching out to the door. Sakura saw the glint of metal beneath his nails, catching in the erratic flashes of light, and went to stop him. It was nothing to her if he wanted to ruin thousands of credits of razor implants trying to get through crumpled metal, but they were wasting time. And then he gestured her away, and she stepped back with a crunch of ground glass. Lasers, Sakura would decide later, as ten black lines drifted slowly like ribbons, curling lazily through metal like the tip of a treble clef as the door opened up in a jagged star. One drifted past her arm, and disappeared. She felt no heat.

Inside the driver's compartment, the window had already shattered, leaving a clear way out for the passengers that were beginning to make their way out ahead of the fire. Sakura leapt out, landed with a scrunch on the sandy floor, and glanced backwards. The boy was still there.

She shrugged impatiently, and gestured that he should follow, not trying to call out when the words would be swallowed up by the sounds of panic anyway. He stayed where he was, and raised his hand slightly, as though in acknowledgement.

Five flashes of metal. Sakura flinched.

* * *

_Sai trains._

_His lasers are set to non-lethal and they would drift harmlessly through metal and flesh and bone, nothing more than a picture show for now. He copies the shapes from the things he has seen. A precise grid of blacklights, like the wire around the complex. Broad beams spreading like headlights diluted across slick roads. A dense haze of smoke. All monochrome, like this city. _

_A milky curl of light like the smudge of a strange and alien galaxy, the colour of strawberry milkshake and cut grass._


	2. Chapter 2

Lux Lacuna

Author's Notes- I've translated the bijuu as being blueprints for various forms of potential doomsday weapons. The non-coding sections of DNA between genes are used as cyphers to hide this information in. A simple AI lives in the electrochemical environment of the brain, and serves to read the code, and protect the host via gene manipulation. The weapons do all sorts of fun stuff according to which deity they're named after- I'll put a list up later if anyone's interested.

Plausible? I don't know, "IT'S THE FUTURE", is my excuse and I'm sticking to it.

Disclaimer – I don't own any of the recognisable characters or concepts. No copyright infringement is intended, and no profit is being made.

* * *

Sakura was called into Tsunade's office a week later, alone.

Her mentor was displeased about something, eyes flashing a dark and hawkish gold as she glowered over her desk at the other two present. One was a weary-looking, heavily-bandaged man that Sakura recognised by name as Danzou. The other was the boy from the underground. His gaze drifted over her without acknowledgement, like the blind sweep of spotlights.

"Sakura," Tsunade said, without formality. "The Sand has been betrayed."

The slight intake of her breath seemed loud among the silence that followed. Tsunade was regarding her over steepled hands, watching for her reaction.

"Akatsuki have almost certainly acquired one of the bijuu, and the host will likely be killed," she said, bluntly. "I thought it best to talk to you before Naruto."

"Yes," she said, for lack of any other words, as she remembered the strange and silent dark-eyed boy from the Sand and the quiet menace around him that Naruto lacked, all the crushing weight of his the bijuu bearing down over him. "Can they extract it-"

"We believe so," Tsunade said, eyes closing briefly before opening again, blazing dark like molten bronze. "I don't need to tell you what may happen if the blueprints have fallen into their hands."

_Helios-_

_-the first of the bijuu, the blueprints for weapons they had to confiscate from the world, wrapped and coded in the meaningless spaces between human genes, a simple AI drifting in the electrochemical prison of a human brain to guard it-_

From what fragments of puzzle-piece information that had slipped between the cracks and been picked up and put together one part at a time, Sakura knew that the codes hidden in _Helios_ would severely affect the damaged atmosphere, concentrating the sun's rays like a magnifying glass. If one of the fragmented countries managed to acquire a weapon like this, they would almost certainly use it. Too long had been spent sniping and spying with splintered forces, the highest technology on the lowest of scales. The weapon they had hidden in a child from the Sand would drown out the desert sun.

"A few agents from the Sand have already gone in pursuit," Tsunade said. "Sasori of the Sand was believed to have had a base nearby. His last relative has been working on locating it for a long time. Based on the trajectories taken after the attack, they have been able to narrow it down significantly."

"Are we to follow?" Sakura asked, eyes flickering to Danzou and the unknown boy with caution.

"Yes. It is dangerous," Tsunade said bluntly. "I don't like it. But as a gesture of good faith to the Sand, we need to send a team and we are stretched thin enough as it is. It's unlikely there will be anything to do at this stage except retrieve the corpse, if possible."

Sakura nodded, slowly.

"And Sakura?" Tsunade said, watching her intently again. "Every step closer to Akatsuki may assist us with finding Orochimaru. He defected from the organisation some time ago. It is likely they wish to see him taken out as much as we do."

Danzou stepped forward, without speaking. Tsunade glanced sideways at him with unmistakeable distrust.

"I've brought a third member in to join you and Naruto," she continued, before Danzou could speak. "Sai will accompany the two of you, as a member of ANBU. He is a long range specialist, and should work well with your style."

"Lasers," Sakura said, nodding at Sai. He regarded her blandly. "We've met."

Danzou gave her a sharp, speculative look over Sai's shoulder. Tsunade did not ask for clarification.

"You will depart tomorrow, after the return of one of the Sand's own agents," she said, shuffling papers dismissively. "I'll send you a full brief. Danzou, can I have a moment with Sakura?"

Danzou left stiffly, taking Sai with him. Tsunade held her hand up, eyes on her computer screen. A minute or two had passed before she spoke, apparently satisfied that they had left the building. "Sakura, do you know which unit Danzou ran?"

"Root, I think."

"Sai was part of that unit," Tsunade told her, her expression closing down. "They were disbanded in name alone, and Danzou is not lending his own agents as a personal favour. Do not trust him, Sakura."

Sakura left, and turned over what she knew of Root later. There was very little public knowledge about them. She knew that they had been Danzou's unit, and they had been officially declared a failure, disbanded, and their agents reassigned. What she had known had left her uneasy. Sakura hadn't been so wrong when she had first suspected that Sai might be an android.

She was edgy that night, waiting to depart. Naruto had his talk with Tsunade. Sakura was unsure how much had been shared with him, but when he emerged from the room, his eyes burned the low and hot blue of a gas jet, and he headed straight to the training rooms with his back stiff and angry. He would be there all night, she expected. Sakura watched him go, and called Sai, reaching up to the small socket behind her ear and feeling the answering tug as he picked up her signal.

"Sai."

To Sakura's surprise, he didn't talk to her remotely as she had expected, a distant electronic voice coming in bursts of encoded signals through the air. She blinked in instantly behind his eyes, her vision switching from the comfortable surroundings of her own room to a surreal scene of stark black swirls on white paper. Sai was painting, a static image of the blacklights she had seen in the underground. A brush hovering above the paper was still glossy with paint. He put it down, carefully, in the slow and dreamy way of someone with a jacked nervous system moving at half speed, and Sakura felt the sudden disorientation she always did riding behind someone's eyes, swimming passively in a mind she could not control.

"Sakura," he greeted her politely. She felt the words shaped at the same time as she heard his voice for the first time, a soft and impersonal monotone seeping into the air, like the pre-set voice of the Konoha computers.

Sakura was silent for a moment, mildly thrown by finding herself linked straight into Sai. Of course she'd been behind someone's eyes before- she and Naruto had linked up countless times in the field- but it was unusual behaviour for anyone she had just met to throw open the doors to their mind in this way.

"What's wrong?" Sai asked. He was now gazing straight ahead out of a window, at the smudgy yellow everglow over the distant civilian cities. He had been in the Konoha complex all along. Sakura had never seen him before in her life.

"Nothing," she said, and paused. "It caught me by surprise, that you let me patch in straight away."

"We're working together," he answered simply. Sakura let it go. She hadn't expected them to work the same way in Root. If Sai hadn't been allowed an identity, he probably didn't feel the same instinctive repulsion she did knowing someone was feeling everything she felt, drifting like a ghost behind her eyes.

"We should train," she said, shaking off the unease and getting back on subject.

Sai nodded, absently. "Correct. You need to learn to stay out of my way."

"And you out of mine," she said, biting back sharp words. "I've booked a room in B60."

They sparred and then worked together against three or four programmes before calling it a night. Their styles clashed instantly. Sai worked from long-range, using lasers from implants wired directly into his altered nervous system. Sakura's style was more raw, no augmentations, everything built from slow and hard training in high gravity and thin atmospheres. Slowly, but built to last, nothing that burned out and needed replacing. And her mind to match, three long years learning how the human body was put together so that she could learn how best to take it apart again.

She tuned her vision up the spectrum to better see the blacklights that sliced through the air like razorwire, until they glowed a pale and ghostly purple. It still took all of her concentration to stay out of the way, always moving in a slow and rhythmic dance through a grid that drifted like spiderwebs around her, and couldn't be felt until it was too late. Sai's nervous system had been jacked, valuable milliseconds gained while chemicals floated in the lost spaces of her synapses. But he was less skilled up close, not knowing how to turn into a blow to shrug it off, or where to hit to blow out a joint or crack bone.

Once she countered him with a pressure point high on the shoulder, and saw him lurch forward off balance as his arm was suddenly numb deadweight swinging at his side, his own nervous system still vulnerable beneath the bluish circuits that showed over the bone. And a second time, she cracked two ribs, sliding sideways between the thin beams of light and feeling the impact shudder up through her compacted skeletal system as his bones cracked like splintery green wood.

And once a pale slice of cold violet light went straight through her chest, numbing her instantly, and she landed hard on the floor with a metallic ringing in her head and a sensation of biting down on crushed and frozen violet blossoms.

"You are too slow," he said, with a vague and sweet android smile. "But they're set to non-lethal."

He reached out help her, and she knocked his hand aside impatiently as she stood up. His expression did not slip, as serene and meaningless as a death mask. He could kill her, with a smile like that.

* * *

_It had been strange in the underground, even before the explosion. _

_Sai was unused to so many people all in one place, and the luxury of simply drifting among them, no one there to watch or to kill. There was too much to follow. A thousand expressions forming, slipping and sliding into each other in a vaguely hallucinatory way. A constant rise and fall of voices that meant nothing, a hundred threads he did not have to follow weaving in and out of each other into a meaningless tapestry. A rapid gunshot clatter of keys on a laptop, hands flickering impatiently in the air as someone spoke into a slim headset._

_Their bonds fell apart very quickly in the panic below the ground. Sai watched a hysterical girl clawing at her boyfriend as she was caught in the twisted wreckage of her seat, and he stumbled away as the flames began to rise. Someone was crawling among the broken glass that had become floor, face gone, bumping blindly into others who pushed them aside. _

_Sai was not on a mission, and he had no orders here. As the flames began to rise, he stood and made his way calmly through the fear-blinded crowd, in no particular hurry._


End file.
